Field of the Disclosure
The present disclosure relates to a developing member used in an electrophotographic apparatus. The disclosure also relates to a method of producing a developing member, a process cartridge, and an electrophotographic apparatus.
Description of the Related Art
A developing method using a non-magnetic mono-component toner is known as an image forming method with an electrophotographic image forming apparatus (hereinafter shortened to “electrophotographic apparatus”), such as a copier or an optical printer. Specifically, a photosensitive drum serving as a rotatable electrostatic latent image carrier is charged with a roller-shaped charging means, such as a charging roller, and the surface of the charged photosensitive drum is exposed to laser light to form an electrostatic latent image. Subsequently, in a developing unit of the image forming apparatus, a toner regulating member applies the toner in a developing agent container onto a developing roller. The electrostatic latent image is developed by the toner at the contact portion between the photosensitive drum and the developing roller. The toner image on the photosensitive drum is then transferred onto a recording material, such as paper, in a transfer unit directly or via an intermediate transferring member. The toner image is fixed to the recording material by heat and pressure in a fixing unit, and the recording material having a fixed image is discharged outside the image forming apparatus.
In many of recent electrophotographic apparatuses, a non-magnetic mono-component developing method is used with a reduction in the size of the main body. A toner is supplied onto a developing roller by an elastic roller (hereinafter, referred to as toner supplying roller) abutted against the developing roller, and is then thinly applied on the developing roller by a toner regulating member. At the same time, toner particles are charged by friction with the toner regulating member and friction with the developing roller. Consequently, the developing roller is rotated while maintaining a certain nip width with the toner regulating member or the photosensitive drum, and the developing roller is therefore required to have a low hardness.
Furthermore, a tendency of demanding for an electrophotographic apparatus having a further reduced size and a high energy saving effect has been increased, and there is a tendency of using a low torque or using a roller having a reduced diameter as the toner supplying roller. However, a reduction in the diameter of the toner supplying roller or slowing the rotation speed for reducing the torque causes another problem of decreasing the amount of the toner conveyed to the developing roller.
As a method for increasing the amount of a toner conveyed to a developing roller, Japanese Patent Laid-Open No. 4-88381 proposes a developing method using a developing agent-bearing member having an elastic surface layer that is made of a conductive elastomer and contains insulating particles dispersed at least in the vicinity of the surface and partially exposed to the surface, and using a toner having a volume-average particle diameter not larger than one-third of the average particle diameter of the insulating particles exposing to the surface. Japanese Patent Laid-Open No. 5-072889 proposes a developing method using a developing agent-bearing member including a continuous phase (sea part) and a discontinuous phase (island part), at least in the surface, formed by blending two or more different amorphous polymers and molding the mixture.